Method of making mercury column thermostats



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Nov. 24, 1953 2,660,005

w. M. SMITH EI'AL METHOD OF MAKING MERCURY COLUMN THERMOSTATS Original Filed Feb. 17, 1949 INVENTORS.

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Patented Nov. 24, 1 953 METHOD OF MAKING MERCURY COLUMN THERMOSTATS William M. Smith, Wheaton, and Benjamin F.

Freeberg and Alva W. Tharp, Chicago, 111., assignors to Vapor Heating Corporation, Chicago, Ill., a corporation of Delaware Original application February 17, 1949, Serial No. 76,954. Divided and this application October 16, 1951, Serial No. 251,608

4 Claims.

This invention relates to the manufacture of liquid column thermostats and has for its principal object the provision of an improved method of embedding one or more contact Wires in the glass tube of such thermostat so as to be engaged by said liquid column to complete an electrical circuit.

Heretofore, considerable difficulty has been experienced in sealing contact wires in the glass tubes of liquid column thermostats so as to provide adequate electrical contact with the thermo-responsive liquid column contained therein. These difficulties have been due primarily to the fact that the contact wires, heretofore used, have extended only to the inner wall of the tube. Consequently, the end only of the wire makes contact with the liquid column in the thermostat tube. Therefore, the area of this contact is frequently reduced by the flow of molten glass over the end of the wire during the operation of sealing the wire in the tube.

In order to facilitate positioning of the contact wire in the thermostat tube, according to the old method, the tube is ordinarily severed and the end of the wire is arranged flush with the inner wall of the central bore of the tube. The severed ends of the glass tube are then rejoined together by heating the glass to a plastic state. In such case the displacement of the molten glass around the contact wire during the sealing operation frequently results in partially or wholly covering the end of the wire so as to materially reduce or Wholly prevent electrical contact of the wire with the liquid column in the tube. Also, the old method of construction frequently results in so extending the contact wire into the bore of the tube as to objectionably reduce the cross sectional area of the bore.

According to the present method, the glass tube of the thermostat is cut at a desired location for the insertion of the contact wire and the Wire, instead of extending only to the surface of the central bore of the tube, extends entirely across the tube on a line which intersects the circumference of the central bore. In this position of the wire its smooth lateral surface, as distinguished from an end surface, will make contact with the liquid column. The smooth lateral surface of the wire, being of larger area than the end area, assists in producing a phenomenon during the manufacture of the thermostat, whereby the liquid column, for example ting of the thermostat may be readily and. ac-

curately separated at the contact wire by flicking the upper end of the tube in a direction to remove the surplus mercury from the central bore.

There has been found that in most instances the. mercury will accurately separate at such con-- tact wire. Apparently the wire provides a uniform scoring of the mercury column at the restricted area of the bore of the tube and also reduces the surface tension at the wire whereby the inertia, during the arcuate flicking movement 1 of the tube, separates the mercury column at the contact wire. m

The opposite ends of the contact wire are connected in an electric circuit so as to heat the wire and melt the surrounding glass sufficiently :to permit the Wire to be partially embedded in one section of the tube preliminary to the reheating and rejoining of both sections of the tube. The preliminary embedding of the con-- tact wire in the glass of the tube fixes the po-.

sition of the Wire relative to the bore of the tube while the position of the wire can be observed and controlled. Therefore, the application of suitable pressure to the wire is efiected to displace the glass adjacent the wire during the- 1 initial softening of the glass, the displacement The said method, for the purpose of convenience,

will be described herein in connection with the manufacture of a mercury column thermostat, but obviously the steps of the method are not necessarily limited to the production of mercury column thermostats.

The invention is illustrated in the accompanying drawing wherein:

Fig. 1 is a View shown partly in elevation and partly in section of a thermostat constructed in accordance with this invention.

Fig. 2 is a view partly in section and partly in elevation illustrating one step in the process of manufacture.

Fig. 3 is a fragmentary sectional view on a greatly enlarged scale taken on line 33 of Fig. 2, and showing also suitable electrical connections with the opposite ends of the thermostat contact wire for passing electrical current throughthe contact wire to heat the glass adjacent the wire. v

Fig. 4. is a fragmentary sectional view of a has part of Fig. 2 illustrating the position of the contact wire in the tube preliminary to the rejoining of the previously severed sections of the thermostat tube, --and Fig. 5 is'a view similar to Fig. 4 but illustrating the previously severed sections of the tube fused together.

Referring first to Fig. 1 of the drawing wherein a complete thermostat is shownt' The -inain -b'ogi .-y of the thermostat tube is designated by the reference numeral Hi. It is formed at its lower end with a bulb H of predetermined size torprovide a storage chamber for the-mercuryused in the thermostat. The main body I is formed with a relatively small central bore {2 which extends from the mercury re'sei vdir ljl its the upper end of the tube and terminates at its upper end in a small bulb l3.

The specific form of thermostat shown includes two contact wiresdesignated l4 and I5. The lower contact wire M is positioned so that it w'ill be in continuous contact with-the mercury column 16; rneupper cohtact "I5 is positioned ae-a reeetermmea location-whereby the mercury column, when*'z'iri'a'irfdedbya predetermined"ternpfeiatiire, win-make doritac't' wi'th the said ='contact l5; "The'contactwires Hl-andit havediaineters dnsiderably -sma11er than the diameter of the b dre "in the tube ar'id extend entirely through the glass tube of the thermostat, -but are "arranged at one side of the longitudinal *c'en'ter so that its'sfno'bth '-'lateral face'will' exterid 'into the central *b'or'e l-2o'f thfe t"ubea distance approximatihg one eigmngor thediam'eter of the wire Whereby'the centrm pdiflt 11 0f the wire "will be *eir'posed to "the interior of -the "said bore 12 an d thereby ro'vide electrical connection Between the contact wires an'd the me'rcurycob or the thermostat. j

he' o pc 'it'e buds if each wire "1'4 ailld l f red or b'thrwis'e inbedded infneli -1 5 the latter of which provide to 'whl ch eiectfiameaa -wires [l 4 li -may He attached. A t

In or'der-to accurately posi-tio'n the wires 1 am; "in "the gla'ss "tube, the tube is severed at thelocatiqnwhere th-e contact wires are to he inserted. "iF'orkifainifle, Wlierlifisertifig' thewire red along the line toprovide ions 1-8'and [9 (see Figs. 2 is arranged in anemon -a1; one side of the be so as to -form a, .1 chord in =th'e ll'ilfr' w alrof the more 1'2, as indic'ated ilfFigsfl 3. The-opposite ds of the-wire T5 are p ff-"s'uitable clamps ans 21, to electrodesffl '3 whereby ahigh'inductfih' burrentispaissed through the contact wire, 15 rby causing 'itjto heatfthe adjacent glass iirltilit *becomes sumeieiiuy *pmsuc 'tO permit the wire, by application of pressure thereto, to j-b'e iiaruauyembeaded "in the glass during the initial softening thereof, as indicatedin Fig. 4. The displacement "of "the gases-ems to draw the glass, in theregion 2'4, outwardly relative fto -tl-ie axis of the bore s'b fasf to maintain a rel'at-ivel'y lar e area 11 or the wireexposjed for contact "with the mercury column. This "preuimnary displacement of glass and fusion 'of the 'wire in t '11 "during thesaid jrejoining of the tubes 'and nifniz es the possibility of 'the hot plastic glass 'g overthe side of the' -Wire-Whic h comfiii'il'lliiaiteswithihe' boie "ofthe *tilbe. nter me tube sections l8 and I9 have been rejoirid' tlie iirsuehca'se bbth ends of the tube are open and esbian is passed through the bore of the tube to prevent the molten glass from flowing into the bore of tl 1e tube. After the contact wires are arranged in their proper position the merbuny res'ervoir'isformed and the tube is filled with mercury. The upper end is then sealed by fusion 19 to lioriipl'etethe thermostat as shown in We claim:

iinproved method of embedding a contact wire in a glass tube so as to communicate with the c'entral'bore of the'tube, which consists in s'evering the tube on a transverse line to pro-- vide two sections, arranging the contact wire against an end --suriace of one section of the tube with an intermediate portion of the wire positioned onalinewhich cuts thecircumference of the bore at one side thereof, passing-electrical current through the wire to heat the wire and adjacent :material of the tube to fuse them together so as -to=-maintain the wire inproper position relative-tothebore oft-he tube, then heating the-adjacent ends of the two sections-of the tube and 'fusing them together, wherebythesaid wire is'embedde'd in the-adja-centfaces of said sections.

1 2. Aniniproved method of embedd-ing a contact wire in a'glass tube so as to communicate with the eentra'l bore "of the tube, which consists in severing the t'ube 0h a transverse line to provide two -sections, arranging the contact wire against an end -surface of one section of the tube and extending entirely across the tube on a line which ciits "the circumference of r the bore at one side =thereof, passing ":electrical current through the wire to' l'ieat --the wire and the adj aeent material :f' the tubeuntil the said material assumes a plastic state, applyingvpressirre to-the wire to embed'it into the" softened glass wall of the tube and t-hereby fix itsqz position -in-the tube relative to "the bore thereof, then heating the-adjacent en'd 'faces of the two sections-of the tube and fusing-them together, whereby thesaid wire is embedded the adjacent faces 1 of said sections andz passingair through the tube to congealthe molten-glass at the wall "of the central bore.

An improved r'nethodof embedding a contact wire "in a glass tube so as to communicate W'ith'the c'entraIbOre 'Qf-the "tube, which consists fin severing the itube on a transverse line to provide two sections, :arranging the 'contact w'ir'e against an end-surface of one section -of the tube =-ana extending entirely across :the tube -on a linewvhich' cuts the circumference of :the bore 'a't'one "side thereof, Rpa-ssing electrical current oug'h th'e'wi-re "to heat the wire 'and'theaclen-t mater-ia-l' of the'stube'soas to soften said ter-ial 'while. pressure is applied :to the :wire in I ir tion to'embedit into *th'eeoftened glass wall-o the tube and to' displace the glass adj acent the was of the hore -0utw ardly-and thereby 'e p(is'e:a =la rge 'area of the side surface of the-Wire to the-'inter'ior of the -bore, then heatirig' tlie adjacent end faces of the two sections o the-tube and fu'sing them t'ogether, whereby the said'wire is"em"bedded in the adjacent-faces (if-said sections.

4. An improved method of embedding a contact wire in a glass tube so as to communicate with the central bore of the tube, which consists in severing the tube on a transverse line to provide two sections, arranging the contact wire against 5 an end surface of one section of the tube and extending entirely across the tube on a line which cuts the circumference of the bore at one side thereof, heating the wire and the adjacent material of the tube to soften said material while pressure is applied to the ends of the wire to embed its intermediate portion into the glass wall of the tube during the initial softening of the glass, then heating the adjacent end faces of the two sections of the tube and fusing them together, whereby the wire is embedded in the adjacent faces of both sections of the tube and communicates with the central bore.

WILLIAM M. SMITH.

BENJAMIN F. FREEBERG.

ALVA W. THARP.

6 References Cited in the file of this patent Number Number UNITED STATES PATENTS Name Date Grogan July 28, 1925 Ronci June 4, 1935 Gustin et al. July 2, 193-5 Eite1 Feb. 1, 1944 Machlett et a1 May 22, 1945 FOREIGN PATENTS Country Date Great Britain Nov. 13, 1942 

